Synaesthesia

Question 1

Cytowic’s (1993) definition of synaesthesia

Answer 1

Sensory incontinence - a disordered merging of senses (what goes in one sense comes out the other).

Question 2

Ward (2012) 3 different sorts of synaesthetic concurrent

Answer 2

Where do synaesthetes see the percept?

1. Object-centred (colour on inducer itself).
2. Egocentric co-ordinates (colour in same place in visual field).
3. ‘Inner screen’ (don’t see the colour in environment - an internal association).

Question 3

Synaesthesia definition

Answer 3

Idiosyncratic links (between an inducer and concurrent) that is very consistent within an individual over time.

Question 4

Buba Kiki effect

Answer 4

Perhaps an example of weak synaesthesia within the normal population (speech sound to shape mapping). Spikey shape = ‘Kiki’ and round shape = ‘Buba’.

Not synaesthesia because it is not idiosyncratic and just hearing the word ‘Buba’ does not automatically trigger the concurrent.

Question 5

Grossenbacher and Lovelace’s (2001) definition of synaesthesia

Answer 5

A conscious experience of systematically induced sensory attributes that are not experienced by most people under comparable conditions.

Question 6

Most common types of synaesthesia

Answer 6

1. Coloured graphemes.
2. Coloured number.

Question 7

Prevalence of synaesthesia

Answer 7

From 1/2000 to 1/20.

Question 8

Synaethesia population

Answer 8

6x more common in women than in men. More common in children than adults.

Question 9

Causes of synaesthesia

Answer 9

Genetic component. Developmental (maybe brain damage and drug-induced) forms of synaesthesia.

Question 10

Kelly (1934) drug-induced synaesthesia

Answer 10

Drug produced colour visions (hallucinations) but not the colour-concurrent nature of synaesthesia (seeing note-colour).

Question 11

Kelly (1934) associative pairing of note-colour

Answer 11

3000 pairings of particular notes with particular colours. Even if people knew the answer, they could not see the colour (synaesthesia was not acquired).

Question 12

Baron-Cohen et al. (1993) consistency of synaesthetes’ associations

Answer 12

Coloured-hearing synaesthetes (see colours in response to words) and controls described the colour images evoked by various words read aloud by the experimenter.

In a surprise test 1 year later, there was a high degree of consistency in images evoked (92%). Consistency in controls 1 week later = 37%.

Question 13

Criterion of consistency

Answer 13

Memory interpretation: not a real sensory blending, but just a very strong memory association.

Criterion of consistency suggests synaesthesia is a genuine, persistent sensory phenomenon (not just memorise - association is automatic; see Baron-Cohen et al., 1993).

Question 14

Hubbard et al. (2005) colour area activation in synaesthetes

Answer 14

Both synaesthete and controls show activation of the grapheme area, but only synaesthetes show activation in the colour area.

Question 15

Theories of synaesthesia

Answer 15

1. Defective pruning.
2. Breakdown of modularity.
3. Cross-wiring.
4. Disinhibition of feedback.
5. Cognitive model (Rich and Mattingley, 2002).
6. A special kind of childhood memory (Hupe and Dojat).

Maybe there is not a single account for explaining every kind of synaesthesia?

Question 16

Defective pruning (Maurer, 1997)

Answer 16

Suggests that synaesthesia results from a partial failure of the normal pruning process that eliminates the connections between the various sensory systems (are we all born synaesthetic?).

BUT not knowing which sense we are exeriencing is not the same as ‘a consistent mapping’ (Deroy and Spence, 2013).

Question 17

Disinhibition of feedback (Grossenbacher and Lovelace, 2001)

Answer 17

Claim that drug-induced synaesthesia is the same as real synaesthesia.

There is feedback between mental images and stimuli that is usually inhibitory. Drugs help let us loose!

Question 18

Cross-wiring (Ramachandran and Hubbard (2001)

Answer 18

The most common synaesthsias (eg. colour-grapheme) relate to brain areas that are anatomically close together.

Cross-wiring of specific brain areas causes excessive proliferation (or defective pruning) of neural connections between adjacent brain maps, such as between area V4 & number area in fusiform gyrus. Heterogeneity between synaesthetes might be caused by cross-wiring at different stages.

Question 19

Rich et al. (2006)

Answer 19

Voluntary colour imagery activates right V4 in everyone, but synaesthetic colour experiences uniquely activate the left medial lingual gyrus in synaesthetes.

Suggests that synaesthetic colours and imagined colours recruit different brain networks, even though both involve internally generated colour.

Question 20

Rich and Mattingley’s (2002) cognitive model

Answer 20

High-level cognitive recognition of inducers? Mostly ignored anyway.

Question 21

Structural connectivity (Bargary and Mitchell, 2008; Hanggi et al., 2011)

Answer 21

There appears to be more structural connectivity of brain areas in synaesthetes. Is this a cause or consequence?

Question 22

Hupe and Dojat’s (2015) critique of synaesthesia.

Answer 22

All neuroimaging studies have been underpowered so most claims of neural basis are as yet unsupported.

Rather than being a neurological anomaly or condition, synaesthesia might just be a special kind of childhood memory.

Question 23

Cohen Kadosh et al. (2009) hypnosis and synaesthesia.

Answer 23

People can be made synaesthetic using post-hypnotic suggestion (colour-number). If seeing a background congruent to the colour-number, people have a lower sensitivity to the number!

Question 24

Bor et al. (2014) adults trained to acquire synaesthetic experiences

Answer 24

Participants consistently coloured books based on their own preferences.

Both reports and experiments seem to suggest that some synaesthesia was developed.

Suggests that we can acquire synaesthesia!